1. Field of the Invention
The present invention relates to an inkjet head that performs printing operation by discharging ink onto a recording medium such as a printing sheet. The present invention also relates to a method of manufacturing the inkjet head.
2. Description of the Related Art
An inkjet head of an inkjet printer includes a flow channel unit and an actuator unit. The flow channel unit includes a plurality of nozzles and a plurality of pressure chambers. Each pressure chamber is connected to a uniquely corresponding nozzle, and ink is discharged from the nozzle when a pressure within the pressure chamber corresponding to the nozzle is increased. The actuator unit includes a plurality of actuators. Each actuator faces a uniquely corresponding pressure chamber when the actuator unit is attached to the flow channel unit. When one of the actuator is selected and activated, the pressure within the pressure chamber uniquely corresponding to the activated actuator is increased and ink is discharged from the nozzle uniquely corresponding to the activated actuator and the pressure chamber.
Japanese Laid-Open Patent Application Publication No. 2003-80709 discloses an actuator unit having a piezoelectric sheet, a common electrode and a plurality of individual electrodes. The piezoelectric sheet is interposed between the common electrode and the plurality of individual electrodes. The common electrode is formed over a plurality of pressure chambers when the actuator unit is attached to the flow channel unit. Each of the plurality of individual electrodes is disposed to face the uniquely corresponding pressure chamber.
In this inkjet head, a conductive adhesive is applied on a side end face of the actuator unit from an upper surface of the flow channel unit. Because the common electrode (internal electrode) of the actuator unit extends to a peripheral border of the piezoelectric sheet, the common electrode is electrically connected to the flow channel unit via the conductive adhesive applied on the side end face of the actuator unit.
When a potential difference exists between the flow channel unit and the common electrode of the actuator unit, moisture from the ink within the flow channel unit is electrolyzed, and hydrogen ions (H+) are consequently generated. If the common electrode of the actuator unit is on the negative side, the generated hydrogen ions move to the common electrode, and the common electrode occludes the hydrogen ions and expands. In this way, when a potential difference arises between the flow channel unit and the common electrode of the actuator unit, the actuator unit can be damaged by the expansion of the common electrode (internal electrode).
In the inkjet head disclosed in Japanese Laid-Open Patent Application Publication No. 2003-80709, because the flow channel unit and the common electrode (internal electrode) of the actuator unit are electrically connected via the conductive adhesive applied on the side end face of the actuator unit, the difference in electrical potential between the flow channel unit and the common electrode of the actuator unit becomes zero. Accordingly, it becomes possible to prevent the actuator unit from being damaged due to migration in the common electrode of the actuator unit.